Process for the preparation of methacrylic acid from methacrolein

ABSTRACT

Catalysts containing tungsten, phosphorus, vanadium, molybdenum, and promoted with at least one of the elements selected from the group selected from Sn, As, Cu, Ce, B, Cr, Fe, Ni, Co, U, Mn, Ag, Ru, Rh, Cd, Sr, In, Zn, and La have been found to be especially effective for the oxidation of unsaturated aldehydes to form the corresponding unsaturated acid.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of the application filed byJames F. White, James R. Rege, Robert K. Grasselli, and Dev D. Suresh,Ser. No. 562,709, and filed on Mar. 27, 1975, now U.S. Pat. No.4,070,397 which is a continuation-in-part of the application filed byJames F. White and James R. Rege, Ser. No. 405,309, filed on Oct. 11,1973, and issued Apr. 1, 1975, as U.S. Pat. No. 3,875,220.

BACKGROUND OF THE INVENTION

A number of catalysts are known for the oxidation of unsaturatedaldehydes to the corresponding acid. See, for example, U.S. Pat. No.3,567,773. Although most of the disclosures suggest that the catalystsare useful for oxidizing methacrolein to methacrylic acid, it has beenfound that the yields of methacrylic acid are low and that specialcatalysts are required in this reaction.

U.S. Pat. No. 3,925,464 discloses a process for preparing unsaturatedcarboxylic acids which comprises reacting the corresponding unsaturatedaldehydes with molecular oxygen in the presence of a catalyst consistingessentially of (a) molybdenum, (b) phosphorus, (c) at least one elementselected from the group consisting of tungsten and magnesium, (d) atleast one element selected from the group consisting of vanadium andbismuth, and (e) oxygen.

SUMMARY OF THE INVENTION

A process has now been discovered for the production of acrylic acid ormethacrylic acid comprising reacting acrolein or methacrolein withmolecular oxygen at a temperature of 200° to 600° C., in the presence ofa catalyst and optionally in the presence of steam, the improvementcomprising using a catalyst of the formula

    A.sub.a W.sub.b P.sub.c v.sub.d Mo.sub.12 O.sub.x

Wherein

A is at least one of the elements selected from the group consisting oftin, arsenic, copper, cerium, boron, chromium, iron, nickel, cobalt,uranium, manganese, silver, rubidium, rhodium, cadmium, strontium,indium, zinc and lanthanum; and

A is about 0.1 to 6; b and d are about 0.1 to about 12; c is a positivenumber less than about 6; and

X is the number of oxygens required by the valence states of the otherelements present.

The catalysts of the invention give high single pass yields tomethacrylic acid and are very stable under the required operatingconditions.

The central feature of the present invention is the catalyst. Thiscatalyst is used in the known process for preparing unsaturated acidsfrom the corresponding aldehydes. The catalysts may be any one of thecatalysts designated by the formula above. The catalyst may be preparedby various techniques that are broadly described in the art and whichare more fully taught by the present specification.

In the catalyst preparations, the various elements of the catalyst arecombined, and the final product is dried normally at a temperature ofabout 100°-150° C. In some preparations, it is helpful to calcine thecatalyst at an elevated temperature of about 300°-600° C., but suchcalcination is normally not required. A number of methods of combiningthe elements of the catalysts are known. The oxides of the elementscould be combined in a slurry, and the resulting slurry refluxed andfinally evaporated to form the catalyst. Alternative and preferredpreparations involve the reflux of a solution of a soluble molybdenum,tungsten and vanadium compound, and then the addition of a phosphoruscompound. The preferred preparations are those that give the bestresults in the Specific Embodiments below.

In the catalyst composition formula above, there are preferred ranges.Preferred are catalysts wherein the phosphorus is present in the rangeof about 0.5 to about 3, i.e., those catalysts wherein c is about 0.5 toabout 3. Also preferred in the present invention are those catalystswhich contain at least one of strontium, cadmium, uranium, cobalt, orchromium.

The catalyst of the invention may be used as pure active ingredients orit may be combined physically with a support material. A number ofsuitable supports are well known in the art. In an experimental study onsupports, it was found that silica, zirconia, diatomaceous earth,titania and alumina supports generally tended to maintain the activityof the catalyst while silica gel and alumina gel tended to reduce theeffectiveness of the catalysts. The catalysts of the present inventioncan be used with any of these support materials.

The catalysts of the invention may also be coated on a massive inertsupport. This coating technique is specifically shown in Examples 8-14.Broadly, this technique involves wetting a porous massive support withwater to the extent that water does not remain on the surface of themassive support and then contacting a powder of the active catalyticmaterial with the massive support while rotating the massive support ina container such as a simple glass jar. Coated catalysts have been foundto be especially effective in this reaction to control the temperatureof the reaction. As indicated above, the process of the inventionwherein the unsaturated aldehyde is oxidized to the correspondingunsaturated acid is well known in the art. Broadly, the reactioninvolves a reactant feed of the unsaturated aldehyde and molecularoxygen over the catalyst. The reactant feed may also contain a diluentwhich is normally steam. The ratio of the reactants in the feed may varywidely. Normally about 0.2 to about 4 moles of molecular oxygen arepresent per mole of the unsaturated aldehyde. The amount of diluentemployed may also vary widely, but normally falls within the range ofabout 1 to about 10 moles of diluent per mole of the unsaturatedaldehyde.

As noted above, the reaction is normally conducted at a reactiontemperature of 200° to 600° C., with temperatures of about 300° to 400°C. being of special interest. The reaction can be conducted undersubatmospheric, superatomospheric or atmospheric pressures at a contacttime ranging from a fraction of a second to ten seconds or more.Reaction can be conducted in a fluid bed or more commonly in a fixed bedreactor.

As noted, the process of the invention is related to the preparation ofacrylic acid or methacrylic acid from the corresponding unsaturatedaldehyde. Of special interest in the invention is the production ofmethacrylic acid from methacrolein because of the very high yieldsobtained and the small amounts of by-products formed.

SPECIFIC EMBODIMENTS EXAMPLES 1-7 Production of methacrylic acid frommethacrolein

Various catalysts of the invention were prepared as described below andtested in the oxidation of methacrolein to methacrylic acid.

EXAMPLES 1 & 2

W₀.8 P₁.3 V₂ Mo₁₂ O_(x)

An aqueous slurry containing 86.2 g. MoO₃, 7.7g. of 85% H₃ PO₄, 7.5 g.V₂ O₃ and 10.8 g. ammonium paratungstate was prepared. The slurry wasrefluxed overnight, evaporated and dried at 120° C. overnight.

EXAMPLES 3 & 4

W₃ P₁.5 V₃ Mo₁₂ O_(x)

An aqueous solution of 11.5 g. 85% H₃ PO₄, 141.2 g. (NH₄)₆ Mo₇ O₂₄.4H₂O, and 53.9 g. of (NH₄)₆ W₇ O₂₄.2H₂ O in 1500 ml. of water. To thissolution was added 23.4 g. of NH₄ VO₃. The resulting slurry was deep redand on a continued heating became orange. The resulting slurry was deepred and on a continued heating became orange. The resulting mixture wasevaporated and dried at 120° C. overnight.

EXAMPLE 5

W₁.2 PV₃ Mo₁₂ O_(x)

A solution of 17.6 g. NH₄ VO₃ dissolved in one liter of water wasprepared. To this solution was added 105.7 g. (NH₄)₆ Mo₇ O₂₄.4H₂ O, andthe mixture was heated with stirring until the solid was dissolved. Tothe resulting solution 5.76 g. of 85% H₃ PO₄ was added, and the solutionturned red. To this mixture was added 16.2 g. ammonium paratungstate andall solids appeared to be dissolved. The catalyst was evaporated todryness, and the resulting solid was dried at 110° C. overnight. Thesolid was ground and screened to a size of 20 to 30 U.S. Standard mesh,and the screened solid was heated at 430° C. for two hours.

EXAMPLE 6

W₁.2 P₂ V₃ Mo₁₂ O_(x)

The preparation of Example 5 was followed except that 11.52 g. of 85% H₃PO₄ was added rather than 5.76 g.

EXAMPLE 7

W₁.2 P₃ V₃ Mo₁₂ O_(x)

The preparation of Example 5 was followed except that 17.30 g. of 85% H₃PO₄ was added rather than 5.76 g.

A reactor was constructed of a 1 cm. inside diameter stainless steeltube having a reaction zone of 20 cc. A mixture of methacrolein, air andsteam was fed over the catalyst in a ratio of 1/6.3/5.2 at thetemperature and apparatus contact time shown in the Table. Thecompositions of these catalysts and the results using these catalystsare shown in Table I. The results are stated as follows: ##EQU1##

                                      Table 1                                     __________________________________________________________________________    Oxidation of Methacrolein to Methacrylic Acid                                 Using Catalysts Containing WPVMo                                                                      Results, %                                                           Reaction Single Pass                                                          Temp.,                                                                             C.T.,                                                                             Yield, Acid                                           Example                                                                            Catalyst  ° C.                                                                        Sec.                                                                              Methacrylic                                                                          Acrylic                                                                            Conversion                                                                          Selectivity                         __________________________________________________________________________    1    W.sub.0.8 P.sub.1.3 V.sub.2 Mo.sub.12 O.sub.x                                           385  4.6 12.7   14.6 70.6  18.0                                2       "      355  4.8 29.9   0.0  65.9  45.4                                3    W.sub.3 P.sub.1.5 V.sub.3 Mo.sub.12 O.sub.x                                             365  4.8 53.2   2.5  82.9  64.2                                4       "      335  5.0 53.4   2.6  75.3  70.9                                5    W.sub.1.2 PV.sub.3 Mo.sub.12 O.sub.x                                                    355  4.8 17.1   2.1  48.4  35.3                                6    W.sub.1.2 P.sub.2 V.sub.3 Mo.sub.12 O.sub.x                                             385  4.5 26.9   3.7  70.0  38.4                                7    W.sub.1.2 P.sub.3 V.sub.3 Mo.sub.12 O.sub.x                                             355  4.7 27.2   3.0  60.3  45.1                                __________________________________________________________________________

EXAMPLES 8-14 Active catalytic material coated on a support

An active catalytic material having the formula W₃ P₂ V₂ Mo₁₂ O_(x) wasprepared by dissolving 706.26 g. of (NH₄)₆ Mo₇ O₂₄.4H₂ O, 280.91 g.(NH₄)₆ W₄ O₂₄.8H₂ O and 78.00 g. NH₄ VO₃ in 3 liters of boilingdistilled water. After three hours, the boiling was discontinued andstirring was continued over the weekend. To the resulting solution wasthen added 76.86 g. of 85% H₃ PO₄, the mixture was boiled down and thesolid dried at 110° C. and calcined at 415° C. for one hour.

This active catalytic powder was coated on Alundum particles sold atNorton SA-5209. The particles were placed in a glass jar and wetted withwater. The water content was reduced to 2.4 g./25 g. of particles withthe flow of air from a hot air gun. The active catalytic powder wasground to a size of less than 50 U.S. Standard mesh. While the glass jarwas rotated on an angle about 17 g. of active powder per 25 g. ofAlundum was added in five separate portions. Between each addition, therotation of the jar was continued from 15-45 minutes. The catalystproduced was an Alundum support with a strongly adhering coat of activecatalytic material. The catalyst was then dried in an oven at 110° C.over the weekend. The resulting catalyst was 39.8% W₃ P₂ V₂ Mo₁₂ O_(x)and 60.2% Alundum. In the same manner, a coated catalyst containing34.8% W₃ P₂ V₂ Mo₁₂ O_(x) and 65.2% Alundum sold as Norton SA-203 and acatalyst containing 20.4% W₃ P₂ V₂ Mo₁₂ O_(x) and 79.6% Alundum SA-203were also prepared. Using the same reactor and feed as shown above,these catalysts were tested in the production of methacrylic acid frommethacrolein. The results are shown in Table 2.

                                      Table 2                                     __________________________________________________________________________    Production of Methacrylic Acid Using                                          W.sub.3 P.sub.2 V.sub.2 Mo.sub.12 O.sub.x alone and in Coated Form                          Reaction  Results, %                                                          Temp.,                                                                             C.T.,                                                                              Single Pass Yield                                     Example                                                                            Catalyst ° C.                                                                        Sec. Methacrylic Acid                                                                        Conversion                                                                          Selectivity                           __________________________________________________________________________     8   Active only                                                                            360  2.6  68.9      92.5  74.5                                   9      "     "    2.5  67.5      93.5  72.2                                  10   39.8% Active                                                                  60.2% Alundum                                                                          380  4.4  65.2      93.3  69.9                                  11      "     365  4.6  59.4      85.7  69.3                                  12   34.8% Active                                                                  65.2% Alundum                                                                          360  4.7  66.2      92.3  71.7                                  13   20.4% Active                                                                  79.6% Alundum                                                                          370  4.6  65.5      86.4  75.8                                  14      "     390  4.5  64.1      92.2  69.5                                  __________________________________________________________________________

EXAMPLE 15 Catalysts of the invention containing optional elements

Various catalysts of the invention containing different elements wereprepared as shown below.

EXAMPLE 15

Rb₀.75 W₃ P₁.5 V₂.25 Mo₁₂ O_(x)

A solution of 141.2 g. (NH₄)₆ Mo₇ O₂₄.4H₂ O and 11.52 g. 85% H₃ PO₄ in 2liters of water was prepared. To this solution was added 53.9 g. of(NH₄)₆ W₇ O₂₄.2H₂ O and then 17.6 g. of NH₄ VO₃. To this mixture wasthen added 7.2g. of RbC₂ H₃ O₂. The mixture was boiled dry, and thesolid was dried at 110° C. overnight.

EXAMPLE 16

Sn₀.5 Cu₂ W₁.2 PV₃ Mo₁₂ O_(x)

A slurry was prepared by the addition to 800 ml. of water 72.0 g. ofMoO₃, 11.36 g. V₂ O₅, 3.13 g. SnO₂ and 5.65 g. 85% H₃ PO₄. The slurrywas heated to reflux with stirring overnight. To the slurry was thenadded 9.19 g. of finely divided tungsten metal and after two hours ofreflux 16.63 g. of cupric acetate was added and refluxing continued for1.5 hours. The slurry was evaporated to dryness and dried at 110° C.overnight.

EXAMPLES 17 AND 18

33.3% Sn₀.5 Cu₂ W₁.2 PV₃ Mo₁₂ O_(x) and 66.7% Alundum

The active catalyst of Example 16 was coated according to the procedureshown in Examples 8-14 to obtain a catalyst having 1/3 active catalyticmaterial and 2/3 Alundum.

EXAMPLES 19 AND 20

Sn₀.5 Cu₂ W₁.2 P₂ V₃ Mo₁₂ O_(x)

The procedure of Example 16 was repeated except that twice the amount ofH₃ PO₄ was used.

EXAMPLE 21

SbW₃ P₂ V₂ Mo₁₂ O_(x)

A solution was prepared using 500 mls. of water and sequentiallydissolving therein 88.3 g. of (NH₄)₆ Mo₇ O₂₄.4H₂ O, 35.1 g. (NH₄)₆ W₄O₁₃.8H₂ O and 9.7 g. NH₄ VO₃. The solution was boiled for five hours andallowed to stand overnight with continuous stirring. To the coolsolution was added 9.6 g. of 85%H₃ PO₄. After about one hour ofstirring, heating was resumed. To this hot solution was added 6.05 g.Sb₂ O₃. The mixture was boiled dry, and the solid was dried in an ovenover the weekend.

EXAMPLES 22-32

The catalysts were prepared in the same manner as Example 21 to givecatalysts of M₁ W₃ P₂ V₂ Mo₁₂ O_(x) (except for rhodium catalyst whichused Rh₀.25, and iron which was Fe₂) by adding the appropriate amountsof the following chemicals in each preparation rather than the antimonycompound: Bi₂ O₃, Ni₂ O₃ ; Cr(C₂ H₃ O₂).H₂ O; Co(C₂ H₃ O₂).4H₂ O;RhCl₃.3H₂ O; Cd(C₂ H₃ O₂)₂.2H₂ O; Fe(NO₃)₃.9H₂ O; AgC₂ H₃ O₂ ;Sr(OH)₂.8H₂ O; UO₂ (C₂ H₃ O₂)₂.2H₂ O; Ce(C₂ H₃ O₂)₃.1.5H₂ O.

These catalysts were employed in the production of methacrylic acid inthe manner shown above, and the results of these experiments are shownin Table 3.

                                      Table 3                                     __________________________________________________________________________     Production of Methacrylic Acid Using Catalysts of the                        Invention Containing Optional Elements                                                                         Single Pass                                                    Optional                                                                            Temp.,                                                                            C.T.,                                                                              Yield of                                     Example                                                                            Catalyst     Element(s)                                                                          ° C.                                                                       Sec. Methacrylic Acid                                                                       Conversion                                                                          Selectivity                   __________________________________________________________________________    15   Rb.sub.0.75 W.sub.3 P.sub.1.5 V.sub.2.25 Mo.sub.12 O.sub.x                                 Rb    370 4.6  47.2     89.0  53.0                          16   Sn.sub.0.5 Cu.sub.2 W.sub.1.2 PV.sub.3 Mo.sub.12 O.sub.x                                   SnCu  355 4.6  17.4     57.0  30.5                          17   33.3% Active of Ex. 16                                                        66.7% Alundum                                                                              "     390 4.4  27.1     63.2  42.9                          18      "         "     365 4.6  23.4     60.7  38.6                          19   Sn.sub.0.5 Cu.sub.2 W.sub.1.2 P.sub.2 V.sub.3 Mo.sub.12 O.sub.                             "     390 4.4  21.6     67.4  32.3                          20      "         "     360 4.6  20.5     63.3  32.4                          21   Sb.sub.1 W.sub.3 P.sub.2 V.sub.2 Mo.sub.12 O.sub.x                                         Sb    "   2.6  68.5     93.8  73.0                          22   BiW.sub.3 P.sub.2 V.sub.2 Mo.sub.12 O.sub.x                                                Bi    370 4.6  61.1     96.0  63.6                          23   NiW.sub.3 P.sub.2 V.sub.2 Mo.sub.12 O.sub.x                                                Ni    380 2.6  61.1     96.1  64.1                          24   CrW.sub.3 P.sub.2 V.sub.2 Mo.sub.12 O.sub.x                                                Cr    405 2.4  47.0     82.8  56.8                          25   CoW.sub.3 P.sub.2 V.sub.2 Mo.sub.12 O.sub.x                                                Co    435 2.3  46.2     83.2  55.5                          26   Rh.sub.0.25 W.sub.3 P.sub.2 V.sub.2 Mo.sub.12 O.sub.x                                      Rh    385 2.6  19.9     64.5  30.9                          27   CdW.sub.3 P.sub.2 V.sub.2 Mo.sub.12 O.sub.x                                                Cd    365 "    63.5     89.6  70.9                          28   Fe.sub.2 W.sub.3 P.sub.2 V.sub.2 Mo.sub.12 O.sub.x                                         Fe    455 2.3  17.5     58.4  30.0                          29   AgW.sub.3 P.sub.2 V.sub.2 Mo.sub.12 O.sub.x                                                Ag    350 2.6  42.7     57.7  74.0                          30   UW.sub.3 P.sub.2 V.sub.2 Mo.sub.12 O.sub.x                                                 U     380 2.5  57.5     91.1  63.1                          31   SrW.sub.3 P.sub.2 V.sub.2 Mo.sub.12 O.sub.x                                                Sr    390 "    55.0     91.4  60.2                          32   CeW.sub.3 P.sub.2 V.sub.2 Mo.sub.12 O.sub.x                                                Ce    425 2.4  39.8     81.3  48.9                          __________________________________________________________________________

We claim:
 1. In a process for the production of methacrylic acidcomprising reacting methacrolein with molecular oxygen at a temperatureof 200° C. to 600° C. in the presence of a catalyst and optionally inthe presence of steam, the improvement comprising using as a catalyst acatalyst consisting essentially of a catalytic oxide of tungsten,phosphorus, vanadium, molybdenum and at least one element selected fromthe group consisting of cobalt, rhodium, cadmium, strontium, indium andzinc , the catalyst composition having the formula A_(a) W_(b) P_(c)V_(d) Mo₁₂ O_(x) wherein A is at least one element selected from thegroup consisting of cobalt, rhodium, cadmium, strontium, indium andzinc; and wherein a is about 0.1-6; b and d are about 0.1 to about 12; cis a positive number less than 6; and x is the number of oxygensrequired by the valence states of the other elements present.
 2. Theprocess of claim 1 wherein A is at least one element selected from thegroup consisting of strontium, cadmium and cobalt.
 3. The process ofclaim 1 wherein c is about 0.5 to about
 3. 4. The process of claim 1wherein A is cadmium.
 5. The process of claim 1 wherein A is strontium.6. The process of claim 1 wherein A is cobalt.
 7. The process of claim 1wherein the catalyst is Cd₁ W₃ P₂ V₂ Mo₁₂ O_(x).
 8. The process of claim1 wherein A is rhodium.